There is something wrong with the physics code which governs loss of grip on the rear wheels with a typical limited-slip diff. This bug has been widely reported and renders most of the street cars both undrivable (unless you fit a race diff and crank up the Accel/Decel to 70/70 or more, plus add much wider rear tires) and totally unrealistic. It really is a shame because the FFB, tire modeling and the physics in FM6 are otherwise sublime.
Specifically, on those cars which have a “0” Decel setting on their LSD, you get ridiculous snap oversteer the moment you lift off the throttle, even at quite low speeds.
On those cars that have a higher Decel setting for their LSD, the problem is much less evident. This makes many of the racing cars a joy to drive by comparison.
Try this:
Drive the Dodge Hellcat in stock trim, using a steering wheel. It is so unstable that any lifting of the throttle, however small, will result in a spin. It’s impossible to modulate because the rears lose ALL grip the moment you lift off. The bug can be alleviated somewhat by fitting a rec-spec diff and dialing up the Decel to 70 or more.
In past Forza’s (4 and 5), there was a progressive loss of grip under these situations. In FM6, it’s all or nothing. In a way, it’s great training to teach you not to lift mid-corner - but it’s too unforgiving right now. Many serious sim review sites have noted this issue.
T10, Please look into this. Something is wrong. The physics in FM5 did not have this issue. Just take the Hellcat to, say, Road Atlanta and enter turn 1 at low speed, then lift off the throttle even slightly. This is a big, nose-heavy muscle car and shouldn’t snap oversteer as if it were a short wheelbase, mid-engine car.